The present invention relates, in general, to rotary clamps having linear actuators, and more particularly, to a rotary clamp having an adjustable piston rod that may be adjusted without the need for disassembling the rotary clamp.
Rotary clamps are known of the type in which linear actuator reciprocating movement is adapted to be translated into rotary movement of a clamp arm. The linear actuator is typically powered by a fluid motor, and a linkage assembly is provided that converts the linear actuator movement into rotary motion of the clamp arm. The linear motion of the linear actuator is often transmitted to the linkage assembly by a piston rod. It is known to provide a threaded engagement between the end of the piston rod and the linkage assembly so that the length of the piston rod and the linkage assembly can be incrementally adjusted to a predetermined rotational angle of the clamp arm. This often requires repeated gauging and measurement of the clamp arm to ensure that the piston rod has been properly adjusted. In addition, the amount of adjustment is limited to the amount of the threaded engagement available for adjustment.
It is also known to utilize telescopic piston rods that provide the use of a pin inserted into corresponding apertures formed in the telescopic piston rod. This known design utilizes an outer shaft connected to the linear actuator and an inner shaft connected to the linkage assembly. The inner shaft is slidably received by an elongated bore in the outer shaft. A pin is removably received by one of a plurality of corresponding apertures in the outer shaft and the inner shaft of the piston rod in order to fixedly position the outer shaft to the inner shaft at a predetermined adjustable length corresponding to a predetermined rotational angle of the clamp arm. The distinct disadvantage with this known design is that the rotary clamp must be disassembled to adjust the length of the telescopic piston rod. The need to disassemble the rotary clamp increases downtime and maintenance time and reduces productivity which are all undesirable factors in an industrial environment.
It would be desirable to provide a rotary clamp that provides for the adjustment of the clamping angle of a clamp arm without having to disassemble the rotary clamp.
The present invention overcomes the above-noted shortcomings by providing an adjustable piston rod for transmitting linear motion from a linear actuator to an internal mechanism of a rotary clamp. The adjustable length of the piston rod corresponds to predetermined rotational angles of a clamp arm wherein the length of the piston rod may be adjusted without having to disassemble the rotary clamp. The adjustable piston rod of the present invention provides a hollow tubular shaft connectable to a linear actuator. A substantially cylindrical rod having a plurality of substantially cylindrical recesses formed on the outside surface of the cylindrical rod is received within the tubular shaft in a telescopic fashion. A cam is pivotally connected to the tubular shaft and provides an aperture formed therein for receiving the cylindrical rod. A torsional spring biases the cam against the cylindrical rod within the cylindrical recesses formed thereon to prohibit the cylindrical rod from moving telescopically relative to the tubular shaft.